ORDER II OPHIUROIDEA—OPHIUREAE 203 
Eucladia, Woodw. Disk granulated. Each of the arms giving off five 
pairs of secondary branches, which 
increase in size outwards. One 
large madreporite present. Silurian ; 
England. 
Onychaster, Meek and Worth. 
Central disk round, small. Arms five, 
simple, long, and covered with a tuber- 
culous integument, in which fine scales 
are embedded. Sub - Carboniferous ; 
North America. 
1 Helianthaster, Roemer. Disk large, 
granulated. Arms sixteen, long, broad, Fig. 329. 
: OT An -5; “ |p Onychaster flexilis, M. and W. Sub-Carboniferous ; 
and covered with a granulated Integu- Crawfordsville, Ind. (after Meek and Worthen). In- 
ment. Lower Devonian ; Bundenbach. dividual of the natural size with rolled up arms; the 
Ke x dorsal covering of the ventral disk is removed, ex- 
1 Euryale, Lam. It is possible that posing the mouth frame. }, Mouth frame enlarged, 
the rough impressions described by viewed from above; c, vertebral ossicle, enlarged. 
5 : A / 
Quenstedt as Euryale liasica, from the Angulatus Bed of Niirtingen (Lias a), 
also belong here. 

Order 2. OPHIUREAE. Muller and Troschel. 
Arms invariably simple, incapable of being rolled up towards the mouth, and, as 
a rule, cased with four series of integumentary plates. Silurian to Recent. 
Mouth shields are well developed in recent forms, one of them serving as a 
madreporite ; but they are absent in all fossil species. 
Sub-Order 1. OPHIO-ENCRINASTERIAE. Stiirtz. 
Arms without ventral shields, the lateral elements of the vertebral ossicles dis- 
junct, and alternately arranged. Mouth shields absent. Disk covered with skin or 
Jine scales, sometimes spinous. Silurian and Devonian. 
To this sub-order belong the following genera :—Protaster, Forbes, from the 
Silurian of England and America. Taeniaster, Billings; Silurian. ugaster, 
Hall; Devonian. Palaeophiura and Bundenbachia, Stiirtz ; Lower Devonian. 
Sub-Order 2. PROTOPHIUREAE. Stiirtz. 
Arms without dorsal, sometimes without ventral shields. Elements of the verte- 
bral ossicles placed opposite one another, and more or less anchylosed. Disk without 
either radial shields, mouth shields, or genital scales. Silurian and Devonian. 
The sub-order is divided by Stiirtz into three groups, comprising the 
following species :— 
(a) Ophiurina Lymani, Stiirtz. Lower Devonian ; Bundenbach. 
(b) Protaster Miltoni, Salter. Silurian; England. Furcaster palaeozoicus 
and Ophiurina Zitteli, Stiirtz. Lower Devonian ; Bundenbach. 
(c) Ophiura primigenia, O. Decheni, and O. Rhenana, Stiirtz. Lower Devonian; 
Bundenbach. 
